DEAR DR. BLONZ: On the subject of sea salts, I am less concerned about contaminants in Himalayan sea salt because it is 3 million years old. However, I am skeptical of, and would not knowingly use, sea salt from the Caribbean and Southeast Asia. We have traveled there a lot to scuba dive. Almost all the islands discharge raw sewage and industrial waste directly into the ocean -- the source of the seawater that can flow into evaporation ponds to make and export table salt. I am concerned that the inorganic contaminants, although present in low concentrations in the seawater, would be concentrated by the process of evaporation to salt crystals. -- B.T.

DEAR B.T.: Your experiences present reasonable sources of concern, but products meant for human consumption must be tested and found safe before being marketed in the U.S.

Seawater is not safe to drink, as it is full of impurities. That would also be the case for salt obtained directly from seawater. Sea salt approved for sale in the U.S. must undergo more than simple evaporation -- typically, a washing process sufficient to remove impurities.

Gourmet salts, like other foods, can come from protected geographical areas in which quality can vary. The output from some regions may be suitable for humans, while others may only produce salts suitable for animals. Note that if a familiar brand indicates it is for animals, it cannot be assumed safe for humans unless expressly stated on the label.

The United States and other countries have geographically protected areas for the production of certain goods. Products from these areas must meet certain standards of quality and include the name of the locale on the label. For more on such U.S. areas, called "geographical indications," see b.link/sggetj. For European Union designations, see b.link/gpmy3s.

The one thing all salts share is that they are predominantly salt (sodium chloride), with only minimal amounts of other minerals -- not nearly enough to count as good dietary sources. While the other minerals can affect how the salt tastes on the tongue, this tends to get lost when used in a recipe.

DEAR DR. BLONZ: One of your recent columns mentioned the coloring used to make "salmon pink." I'm surprised you didn't reference the Monterey Bay Aquarium's Seafood Watch program. It provides a wealth of information about which fish -- farmed or wild -- is best to eat, which to avoid and why. You can explore seafood and the industry from different angles and read the stories behind some fishery operations. The goal is to keep the oceans, and us, healthy. The program even provides printable pocket guides to take to the market to help us make the best choices around sustainable seafood buying and eating. It's an excellent resource, and makes for some eye-opening reading. -- L.M.

DEAR L.M.: My thanks for mentioning Seafood Watch (seafoodwatch.org). It is very informative, but relies on generalities about different types of fish. There can be good, bad and ugly players all over, so it is important to check about individual purveyors to see if they are doing it right. (Having a trusted fishmonger do this for you is a plus.)

On a related note, I recommend visiting the Monterey Bay Aquarium, as it provides a unique educational experience for the whole family.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: I have a question about minerals and absorption. Let's say that our body can only absorb 50% of the minerals in a supplement, and that supplement label shows it supplies 100% of the RDA. Does that mean you must take twice the dose to absorb the RDA? How does this apply to food labels? -- S.M.

DEAR S.M.: Dietary recommendations consider the body's absorption efficiency -- they reflect the average amount an individual should eat daily to satisfy their requirements. If, for example, science determines that the average body should have 300 milligrams of a particular mineral every day, and if the research indicates that we absorb only about 30% of this mineral in our food, then the recommended dietary allowance (RDA) for that mineral would be 1,000 milligrams per day (30% of 1,000 = 300). This allows us to take RDA figures literally. Still, an additional heads-up is needed in relation to your question.

Foods and dietary supplements make use of the Facts labels (Nutrition Facts and Supplement Facts), and this system uses the Daily Value (DV), not the RDA. The RDA is based on research data to establish requirements according to gender and age. The DV, by contrast, presents one set of numbers for all adults. The intended role of the DV was to help consumers decide between foods by providing a way to check which provides the preferred nutrient profile. DVs are based on the RDAs, but are not as precise. Read more on Daily Values at b.link/mq2sqr.

DEAR DR. BLONZ: You debunked the ice hack, but it left me wondering whether there is a potential for drinking too much water that could possibly hurt the body or the kidneys. -- P.O.

DEAR P.O.: You can overconsume most things, and water is no exception. With water, it is referred to as overhydration, which can progress to water toxicity. That's right: pure water, the toxin!

This risk is based on the fact that the body cannot eliminate pure water. An amount of electrolytes, present in all bodily fluids and essential for nerve transmission, gets shown the door with every drop of urine and sweat. Sodium, the main element in salt (sodium chloride), is our primary electrolyte in body fluids and tissues; this explains why perspiration has its salty taste. Our body requires specific concentrations of items to work. Overhydration forces the elimination of the excess to bring concentrations back into line, which can drain sodium to dangerous levels (hyponatremia).

Low sodium becomes particularly problematic for folks with cardiac issues, such as congestive heart failure, but taking in too much water also becomes a serious issue for those with existing kidney disease. Plain water is the culprit; there is less of a risk when water comes with electrolytes, such as in well-made sports drinks. For more information on drinking water, see the National Library of Medicine info page at b.link/7b55s4.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: I remain confused as to why organic and holistic food makers don't use flavors from the food that is the origin of that flavor, such as using the compound in real strawberries to flavor other strawberry-flavored foods. I see "natural flavors" listed, but I know these are not the same. How do natural flavors differ from artificial flavors? -- R.Q., Seattle

DEAR R.Q.: Whether in fresh, whole foods or highly processed ones, flavors come from distinct combinations of chemicals. Making them involves high-tech science, complete with chemists and secret formulas designed to convince your palate you've got the real thing.

The direct approach might sound preferable, but it's risky commercially. Plant flavors are potent but low in concentration, being made and sustained for a specific reason: signaling when its seeds are fully formed and ready for action. The timing is important, as animals eating fruits and then passing the seeds through their GI tracts are one way that seeds get distributed in nature. The system fails if seeds get consumed before they are ready; this explains why plants evolved to keep poachers away from their immature fruit -- with undesirable flavors and indistinct aromas and colors.

Extracted plant flavors and aromas are less stable, can break down during processing and storage, and/or can interact negatively with other ingredients or the packaging material. There's also a question of uniformity, as fresh foods vary from producer to producer and season to season. Biting into a less-than-sweet fresh strawberry wouldn't stop you from eating other fresh strawberries, but a bad taste in a strawberry-flavored processed food made with "natural strawberry flavor" and "other natural flavors" might.

There's an interest in having "natural" or "no artificial anything" on food labels. To label a flavor "natural" requires that its components come from natural sources. While some flavor from the strawberry would need to be in "natural strawberry flavor," that's not so for products labeled as "naturally flavored" or "with other natural flavors."

Even if scientists could control the inconsistencies of food flavors, the supply couldn't meet the demand. If, for example, the manufacturer had to use real strawberries to make strawberry Jell-O, the world supply of strawberries could be exhausted in days.

Flavor chemists isolate and identify the compounds that are responsible for a flavor. If making an artificial flavor, the chemists can develop a synthetic version of the actual flavor. If the label is to read "natural" but the flavor is not naturally found in the actual food, the chemist would combine different naturally occurring substances to create a flavor impression that matches the target flavor. Companies use tasting panels to help them identify flavor combinations that work best for their target consumers; this also means that one company's "natural" flavor may taste nothing like another's.

Ironically, one's sense of taste is not always the best way to identify a natural flavor. One processed food product flavored with a higher percentage of real strawberries might taste inferior to another with a better formula in its "other natural flavors."

Ultimately, a good advertising campaign might persuade a consumer to try a product, but repeat business and ultimate success in the marketplace will depend on how it tastes. In today's marketplace, the only way to avoid the issue of flavor additives is to stick with fresh, whole foods.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.